1. Technical Field
The present invention relates to ink jet recording apparatuses.
2. Related Art
In ink jet recording, ink droplets are propelled onto a recording medium such as paper to produce a print. Recent revolutionary advances in ink jet recording technology have enabled the use of ink jet recording apparatuses in the field of high-resolution image recording (image printing), where photography and offset printing have so far been used.
In an ink jet recording apparatus, ejected ink increases in viscosity (thickens) as water and other volatile components evaporate therefrom. Such thickened ink clogs nozzles, which causes problems with ejection of ink. In recent ink jet recording, ink droplets are ejected in extremely small amounts, i.e., several picoliters, for high-resolution recording. Accordingly, ink is ejected from smaller nozzles with lower energy. Because of the smaller nozzles and the lower ejection energy, nozzle clogging has a greater impact on ejection of ink. In addition, bubbles may enter the nozzles and ink supply channels, which causes problems with ejection. Furthermore, in ink jet recording on recording media such as paper and fabric, large amounts of fiber and paper dust are produced during paper feed operation. These substances, as well as ambient dust and extremely small ink droplets occurring during ejection, may be deposited on a surface of an ink ejection print head in which nozzles are formed (hereinafter referred to as “nozzle surface”). If foreign matter such as ink, paper dust, fiber, and ambient dust is deposited on and around the nozzles, it blocks normal ejection of ink.
To reduce or eliminate problems with ejection due to ink thickening, entry of bubbles, and deposition of foreign matter on the nozzle surface, ink jet recording apparatuses having a wiper mechanism (recovery mechanism) have been proposed.
For example, JP-A-2006-142804 discloses an ink jet recording apparatus having a cleaning mechanism including a wiping blade. This reference discloses that fine particles are distributed over the surface of the wiping blade to reduce the friction coefficient between the wiping blade and the head, thereby protecting the nozzle surface.
As a compact, low-cost ink jet recording apparatus with high weatherability, durability, and reliability, JP-A-2009-101630 discloses an ink jet recording apparatus including an applying unit that applies a treatment liquid to a recording head or a wiper member.
However, the wiping blade disclosed in JPA-2006-142804 provides poor cleaning performance when used to clean a stepped nozzle surface. Specifically, when the wiping blade is used to clean a stepped nozzle surface formed by a nozzle plate and a nozzle plate cover, the wiping blade is moved while scraping off ink outward from the center of the blade. Although the wiping blade leaves no ink near the nozzles, ink builds up around the wiping blade. In particular, scraped ink builds up at the step between the nozzle plate and the nozzle plate cover. Such ink build-up grows and eventually interferes with the lip surface of the cap, which prevents tight capping. For an ink jet recording apparatus configured for recording with an ink containing an inorganic pigment (hereinafter referred to as “inorganic-pigment containing ink composition”), simply using a treatment liquid as disclosed in JP-A-2009-101630 results in damage to a liquid-repellent film due to the inorganic pigment during cleaning and poor cleaning performance. In addition, the treatment liquid enters the nozzles together with bubbles and aggregates the pigment, which causes problems with ejection, and the liquid-repellent film cannot be sufficiently protected because the pressing force is not considered. Damage to the liquid-repellent film results in unstable ejection of ink, which causes problems such as irregular dot landing. FIG. 6A illustrates an example of an intact liquid-repellent film. FIG. 6B illustrates an example of a slightly damaged liquid-repellent film, which does not significantly affect ejection. FIG. 6C illustrates an example of a considerably damaged liquid-repellent film, which significantly affects ejection. The condition illustrated in FIG. 6C can result from repeated cleaning operations under particular conditions with the use of an ink containing an inorganic pigment.